Diffusion ring for limiting hydraulic ram travel

ABSTRACT

A porous sintered metal diffusion ring is used with one or more drain holes in a hydraulic jack to limit the power stroke of the ram.

v United States Patent Inventor Appl. No.

Filed Patented Assignee Lyle L. Arnes Racine, Wk. 843,366

July 22, 1969 Aug. 24, 1971 DIFFUSION RING FOR LIMITING HYDRAULIC RAM TRAVEL 5 Claims, 1 Drawing Fig.

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F151) 21/04,F01b 31/18 r f) I Primary Examiner-Paul E. Maslousky Attorney-Harness, Dickey and Pierce ABSTRACT: A porous sintered metal diffusion ring is used with one or more drain holes in a hydraulic jack to limit the power stroke of the ram.

DIFFUSION RING FOR LIMITING HYDRAULIC RAMv TRAVEL BACKGROUND OF THE INVENTION In hydraulic jack or ram devices it is considered necessary to automatically limit outward movement of the ram on its power stroke by means of internal structure so that the user does not inadvertently destroy the jack and drop the load being raised. Generally speaking, three methods of stroke limitation are in use. First is a valve structure in the ram which is actuated at the end of the stroke to permit pressure to flow to the reservoir. Secondly, the jack structure itself is made sufficiently strong so that an ordinary abutment stop serves to define the end of the stroke. The third method is to provide a small weep hole" which is uncovered by the ram packing to connect the pressure side of the ram to the reservoir.

Each of these methods has important disadvantages. The internal valve structure is quite expensive and may preclude the use of an extension screw inside of the ram. The use of the jack structure itself as a stop results in very high forces on the cylinder, ram and ram gland parts, which limit the type of seals that may be employed, tend to'cause leakage, and require a pressure relief valve in the hydraulic circuit. The use of a weep hole" results in rapid, fatal destruction by abrasion of the ram packing which is extruded into the hole by internal pressure (usually 10,000 p.s.i.) and destroyed, sometimes on one cycle of the jack.

BRIEF SUMMARY OF THE INVENTION It is the purpose of this invention to provide an improved type of hydraulic jack or ram power stroke limiting means.

The invention accomplishes this by the use of one or more drain passages that connect the ram cylinder to the reservoir. On the ram side, these passages are covered by a porous diffu sion ring which contains a mass of minute passages that together provide a total flow capacity that is adequate to relieve the pressure on the ram. However, the pore size of the ring is small enough to avoid rapid abrasion of the ram packing.

Thus, more generally, the invention provides a low abrasion bearing and flow control member for use with a liquid passage in a hydraulic device.

DESCRIPTION OF THE DRAWING The drawing is a side elevation, partly in section, of a hydraulic jack or ram device embodying the invention.

DETAILED DESCRIPTION OF THE INVENTION The jack 1 has an outer cylinder or housing =3 which is secured to a base 5. Coaxial with and inside of the cylinder 3 is a ram cylinder 7 that is also secured to the base as by the threaded connection 9. The annular space between the cylinders 3 and 7 comprises a reservoir 11 for hydraulic liquid and the longitudinal space inside of the cylinder 7 constitutes the chamber 13 in which the ram 15 reciprocates. The ram 15 has an extension screw 17 threaded internally into it from its top end 19 which provides a means for manually extending the useful longitudinal reach of the jack 1.

The top end 19 of the ram projects out of the jack 1 by way of a suitable packing construction which may include a gland nut 21, a packing ring 23, and a washer 25, the latter engaging the top end of the cylinder 7. The cylinder 7 and the outer housing 3 are interconnected at the upper ends by means of the tank nut 27 which is crushed against the top end of the cylinder 3 and threaded on the top end of the cylinder 7, as seen at 29. It is also internally threaded to receive the gland nut 21.

Adjacent the bottom of the tank nut 27 the ram cylinder 7 is provided with several (preferably four) drain holes 31 which open into the reservoir 11. The inside or inlet ends of the drain holes 31 open into a counterbore 33 in the top end of the cylinder 7 in which is fitted the porous diffusion ring or sleeve of this invention 35. The washer 25 bears on the top end of the ring 35 to prevent its movement. The porous sleeve 35 covers the inner ends of the drain holes 31 and forms the inlet for them as well as forming a portion of the surface or wall of ram chamber 13.

The lower pressure end of the ram 15 contains a suitable bearing and packing structure 36 including the flexible packing member 37, which because of the present invention, may even be formed of rubber. A pump mechanism 39 operated by a handle means including the handle socket 41 is provided in the base 5 along with-suitable hydraulic valves and passages represented by the reference numeral 43 to enable liquid to be taken from the reservoir 11 and supplied at high pressure to the bottom face of the packing 37 thereby causing the ram 15 to move out of the cylinder 7. A release valve 45 in the base 5 enables the operator to connect the pressure side of the ram directly to the reservoir 11 so that the jack may be lowered at a desired rate. Suitable filters (not shown) are used in the hydraulic system to eliminate solid impurities in the hydraulic oil.

In operation, when the packing 37 passes beyond the end of the porous ring 35, high pressure hydraulic liquid acting on the bottom of the packing in the chamber 13 will bleed through the ring into the drain holes 31, the magnitude of this flow increasing as more and more of the ring 35 is uncovered, Thus, pressure on the face 37 is dissipated by flow from the chamber 13 through the ring 35 and drain holes 31 into the reservoir 11 so that the outward travel of the ram 15 is terminated.

The diffusion ring 35 is formed of a low density, high porosity material such as the sintered metals, preferably bronze, and has an average pore size of about 40 microns or less, preferably 20 microns. With a ZO-micron pore size the flow rate is adequate to limit ram travel and abrasiveness is low enough so that even rubber may be used to form packing 37. If a more abrasion resisting packing material is used, such as leather, the pore size may be increased toward the 40 micron average size so as to increase the venting or flow rate.

Thus, the sleeve 35 serves as a porous, low abrasion bearing or wall surface for the ram packing which provides a filtered flow of pressure liquid at a desired rate from a pressure chamber to a reservoir.

I claim:

1. In a hydraulic device, means providing first and second liquid chambers and a wall separating said chambers, said wall having a liquid flow passage connecting said chambers, a slidable member in the first of said chambers having a portion engaging the surface of the wall and movable across said passage during usage of the device, and a high porosity diffusion member set into said wall to form a part of the surface thereof in said first chamber and slidably engaged by said slidable member portion, said diffusion member covering said passage so that liquid flowing through the passage flows through the diffusion member.

2. A device as set forth in claim 1 wherein the area of the diffusion member which forms a part of the wall surface is materially greater than the cross sectional area of said flow passage.

3. In a hydraulic ram device, a reservoir, means providing a ram chamber having a wall, a ram in the ram chamber having a pressure end sliding on said wall, means providing a stroke limiting drain passage having an outlet in the reservoir and an inlet in the ram chamber, said inlet being located adjacent the position occupied by the pressure end of the ram when the ram has moved to substantially the desired termination point for ram travel, and a low density, high porosity diffusion member forming the inlet for said drain passage and also forming a portion of the surface of the ram chamber wall engaged by said sliding pressure end, said diffusion member being materially greater in area than the cross-sectional area of said drain passage, said ram chamber wall having a recess, said member being seated in said recess.

4. A device as set forth in claim 3 including gland means for the ram and wherein said recess opens out of one end of the wall, said gland means pressing on said member to hold it in said recess.

5. 40 device as set forth in claim 4 wherein said diffusion 

1. In a hydraulic device, means providing first and second liquid chambers and a wall separating said chambers, said wall having a liquid flow passage connecting said chambers, a slidable member in the first of said chambers having a portion engaging the surface of the wall and movable across said passage during usage of the device, and a high porosity diffusion member set into said wall to form a part of the surface thereof in said first chamber and slidably engaged by said slidable member portion, said diffusion member covering said passage so that liquid flowing through the passage flows through the diffusion member.
 2. A device as set forth in claim 1 wherein the area of the diffusion member which forms a part of the wall surface is materially greater than the cross sectional area of said flow passage.
 3. In a hydraulic ram device, a reservoir, means providing a ram chamber having a wall, a ram in the ram chamber having a pressure end sliding on said wall, means providing a stroke limiting drain passage having an outlet in the reservoir and an inlet in the ram chamber, said inlet being located adjacent the position occupied by the pressure end oF the ram when the ram has moved to substantially the desired termination point for ram travel, and a low density, high porosity diffusion member forming the inlet for said drain passage and also forming a portion of the surface of the ram chamber wall engaged by said sliding pressure end, said diffusion member being materially greater in area than the cross-sectional area of said drain passage, said ram chamber wall having a recess, said member being seated in said recess.
 4. A device as set forth in claim 3 including gland means for the ram and wherein said recess opens out of one end of the wall, said gland means pressing on said member to hold it in said recess.
 5. 40 device as set forth in claim 4 wherein said diffusion member and recess are annular and the member is formed of sintered metal having an average pore size of about 40 microns or less and said ram pressure end has a flexible, nonmetallic packing slidable over the diffusion member. 